t = -2:0.01:2; T = [15,25,51,101]; for k = 1:length(T) a=0; for n = 1:2:T(k) b=exp(1i*n*pi*t)/n; a=a+b; end y=2*a/(1j*pi); x=0.5*square(pi*t); figure; p=plot(t,real(y),t,x); axis([-2,2,-0.8,0.8]); set(gca,'XTick',-2:1:2) set(gca,'YTick',-0.8:0.4:0.8) set(gca,'XTickLabel',{'-2','-1','0','1','2'}) set(gca,'YTickLabel',{'-0.8','-0.4','0','0.4','0.8'}) xlabel('自变量') ylabel('函数值') titlemsg=sprintf('吉布斯现象N=%d的合成波形',T(k)); title(titlemsg) text(0,-0.5,'\leftarrow 方波函数','HorizontalAlignment','left') set(gcf,'Color','w') hold on end

Null is a term that represents the absence of a value or data in a database or programming language. It can be used to denote a missing or undefined value, empty space, or an unknown value. In programming languages, null is often used to indicate an uninitialized variable or a pointer that does not point to any valid memory address. In databases, null is used to represent a missing or unknown value in a field.

相关问题

补全代码 sigma = 1; x = -2:0.01:2; y = -2:0.01:1.5; [X, Y] = meshgrid(x, y); %X = X; %Y = Y; P_E = X + sqrt(3) * Y + sigma/2 * (X.^2+Y.^2-1).^2; figure subplot(121) contour(X, Y, P_E, 80) sigma = 8; x = -2:0.01:2; y = -2:0.01:1.5; [X, Y] = meshgrid(x

以下是代码的完整版：

sigma = 1;
x = -2:0.01:2;
y = -2:0.01:1.5;
[X, Y] = meshgrid(x, y);
P_E = X + sqrt(3) * Y + sigma/2 * (X.^2+Y.^2-1).^2;

figure
subplot(121)
contour(X, Y, P_E, 80)

sigma = 8;
x = -2:0.01:2;
y = -2:0.01:1.5;
[X, Y] = meshgrid(x, y);
P_E = X + sqrt(3) * Y + sigma/2 * (X.^2+Y.^2-1).^2;

subplot(122)
contour(X, Y, P_E, 80)

这段代码是用MATLAB实现的，其中包含两个子图，分别对应着不同的惩罚系数sigma。首先，我们在一个二维网格上计算出函数P_E的值，然后通过contour函数绘制出等高线图。其中，sigma=1和sigma=8分别对应着左右两张子图。可以看到，当sigma变大时，等高线图变得更加陡峭，目标函数的极小值也变得更加明显。

用matlab画出t=-3:0.01:3; f = exp(-2 * abs(t))的频谱

您可以使用MATLAB中的fft函数来计算信号的频谱，代码如下：

t = -3:0.01:3;
f = exp(-2 * abs(t));
N = length(f); % 信号长度
Fs = 1/(t(2)-t(1)); % 采样频率
f_fft = fft(f)/N; % 计算FFT并归一化
f_fft_shift = fftshift(f_fft); % 将0频率移到中心
f_axis = linspace(-Fs/2,Fs/2,N); % 频率轴
plot(f_axis,abs(f_fft_shift)); % 绘制频谱图
xlabel('Frequency (Hz)');
ylabel('Magnitude');
title('Frequency spectrum of exp(-2*|t|)');

运行以上代码后，可以得到exp(-2 * abs(t))的频谱图。注意，由于FFT输出的是复数，因此我们需要取绝对值来得到信号的幅值谱。频谱图如下所示：